Efficacy, safety and prognostic factors in patients with refractory metastatic colorectal cancer treated with trifluridine/tipiracil plus bevacizumab in a real-world setting

We evaluated the efficacy and safety of trifluridine/tipiracil (TAS-102) plus bevacizumab in treating refractory metastatic colorectal cancer (mCRC) in a retrospective, observational study. Patients refractory or intolerant to standard therapies received TAS-102 (30–35 mg/m2 twice daily on days 1–5 and days 8–12 every 28 days) plus bevacizumab 5 mg/kg on days 1 and 15. Clinical and pathological characteristics, overall response rate (ORR), disease control rate (DCR), overall survival (OS) and progression-free survival (PFS) data were collected and analysed. Thirty-five patients were treated from July 2019 to October 2021 (median age 64 years). The majority of patients (68.6%) were receiving TAS-102 plus bevacizumab as third-line treatment. Patients received a median of 4 (range 2–15) cycles of treatment. Among 31 patients evaluable for response (88.6%), ORR and DCR were 3.2% and 51.6%, respectively. After a median 11.6 months’ follow-up, median PFS was 4.3 (95% confidence interval [CI] 3.4–5.1) months and median OS was 9.3 (95% CI 6.6–12.1) months. The most common grade 3–4 toxicities were neutropenia, asthenia and nausea/vomiting, and there were no treatment-related deaths. This real-world study confirms the efficacy and safety of TAS-102 plus bevacizumab in patients with refractory mCRC.

www.nature.com/scientificreports/ aggressive disease (i.e. ≥ 18 months since metastatic disease diagnosis) as having improved survival outcomes with TAS-102 monotherapy 7 . The survival benefits with TAS-102 monotherapy are modest and there is a need for improved treatment options in patients with refractory mCRC. Several phase I/II and phase II studies have investigated the efficacy and safety of TAS-102 in combination with bevacizumab [8][9][10][11][12][13] . These studies included the single-arm Japanese C-TASK FORCE study in 25 patients with refractory mCRC, which reported a centrally-assessed median progression-free survival (PFS) of 3.7 months and a median OS of 11.4 months with TAS-102 plus bevacizumab 9 . In a Danish randomised study in 93 patients with refractory mCRC, TAS-102 plus bevacizumab was associated with significantly improved median PFS (4.6 vs 2.6 months, hazard ratio [HR] 0.45, p = 0.001) and median OS (9.4 vs 6.7 months, HR 0.55, p = 0.028) compared with TAS-102 monotherapy 10 .
Previous retrospective studies of Japanese patients with refractory mCRC have also indicated that the TAS-102 plus bevacizumab combination provides significant survival benefits compared with TAS-102 monotherapy in routine clinical practice [14][15][16] ; however, real-world data on the use of TAS-102 plus bevacizumab in non-Asian populations are limited. The aim of this real-world study was to evaluate the efficacy, safety and prognostic factors of TAS-102 plus bevacizumab in patients with refractory mCRC in routine clinical practice in Spain.

Results
Population characteristics. Thirty-five patients were treated with TAS-102 plus bevacizumab between July 2019 and October 2021 and were included in this study. Patient characteristics are summarised in Table 1 Efficacy. In total, 31 of 35 patients (88.6%) were evaluable for response; two patients (5.7%) were not evaluable due to an early death, and two patients (5.7%) had response assessment pending at the time of the analysis. After a median follow-up of 11.6 months, 15 patients (48.4%) had PD, one (3.2%) had achieved partial response (PR) and no patients had complete response (CR) ( Table 2). The overall response rate (ORR) and disease control rate (DCR) were 3.2% and 51.6%, respectively.
In the univariate regression analysis, prognostic factors associated with significantly improved OS were the absence (vs presence) of peritoneal metastases and grade 1-2 (vs grade 3) tumour histological grade ( Table 3). The absence of peritoneal metastases was also associated with significantly improved PFS, whereas < 3 (vs ≥ 3) metastatic sites was associated with significantly worse PFS.
Safety. The most common adverse events (AEs) of any grade were neutropenia (74.3%), asthenia (65.7%), anaemia (54.8%) and thrombocytopenia (34.3%) ( Table 4). The most frequent grade 3-4 AEs were neutropenia (45.7%), asthenia (17.1%) and nausea/vomiting (8.6%). There were no reports of febrile neutropenia and no treatment-related deaths. Neutropenia was managed by reducing the dose of TAS-102 in five patients (38.1%) and administration of G-CSF prophylaxis in five patients (33.3%), while in the other patients, treatment was delayed until recovery. In this study, 37.1% of patients required a dose reduction of TAS-102 (20% required one dose level reduction (-5 mg/m 2 ), and 17.1% required two dose level reduction (-10 mg/m 2 ) from baseline dose level. No patients required dose reduction or discontinuation of bevacizumab.

Discussion
In this real-world study of TAS-102 plus bevacizumab treatment in patients with refractory mCRC, efficacy and safety data were generally consistent with those of previous clinical studies, including the Japanese C-TASK FORCE study 9 and the Danish phase II study 10 . The ORR in our study (3.2%) was slightly higher than that reported in C-TASK FORCE (0% by central assessment) 9 and the Danish study (2%) 10 , whereas the DCR was slightly lower in our study (51.6%) than in earlier studies (64% and 67%, respectively) 9,10 . In our study, the median PFS (4.3 months) was similar to that reported in the earlier studies (3.7 and 4.6 months, respectively), while the median OS (9.3 months) was similar to that of the Danish study (9.4 months) 10 , but slightly lower than in C-TASK FORCE (11.4 months) 9 .
The efficacy of TAS-102 plus bevacizumab in our study was also generally comparable with that reported in previous real-world retrospective studies of Japanese patients with refractory mCRC, in which the median PFS with TAS-102 plus bevacizumab was 3.7 months 16 or 4.4 months 14 , and the median OS ranged from 8.6 to 14.4 months [14][15][16] .
Patients with refractory mCRC often have poor prognosis 17 . In our real-world study, 22.9% of patients had an ECOG PS of 2 and therefore may be more representative of patients with refractory mCRC in routine clinical practice than the previous C-TASK FORCE and Danish clinical studies, which excluded patients with ECOG PS of 2 9,10 . In the previous Japanese real-world studies of TAS-102 plus bevacizumab, the proportion of patients www.nature.com/scientificreports/ with ECOG PS of 2 (or modified Glasgow prognostic score of 2) was also much lower (1.4-4.8%) 14-16 than in our study. Therefore, our study indicates that TAS-102 plus bevacizumab continues to be effective in patients with refractory mCRC and poor performance status scores.
In the univariate analysis of prognostic factors for survival, our study showed that OS and PFS were significantly improved in patients without peritoneal metastases, and those with low tumour histological grade had significantly improved OS. However, patients with low tumour burden (< 3 metastatic sites) had significantly worse PFS compared with those with ≥ 3 metastatic sites. Although this result seems counterintuitive, the low www.nature.com/scientificreports/ tumour burden may be an indicator of treatment intensity or the finding may be a statistical artefact associated with the small population size of our study. Another study found no difference in survival outcomes between patients CRC with three versus four metastatic sites 18 . Moreover, a large database analysis of the correlates of survival showed that the organ affected by metastasis was an important determinant of survival 19 . Further research is needed to determine whether it is the number of metastatic sites or the organs affected by metastases that has the greatest impact on survival outcomes. Previous studies have identified other baseline prognostic factors associated with improved clinical outcomes with TAS-102 (either as monotherapy or combined with bevacizumab), including modified Glasgow prognostic score 20 , the Tabernero prognostic factors [i.e. low tumour burden, less aggressive disease (≥ 18 months since diagnosis of metastatic disease) and liver metastases] 7 , high lymphocyte-to-monocyte ratio (≥ 3.18) 21 , and the TAS-RECOSMO predictive model [i.e. general status, neutrophil-to-lymphocyte ratio, KRAS, NRAS and BRAF mutation status, carcinoembryonic antigen (CEA) and alkaline phosphatase (ALP) levels, and time since metastatic disease diagnosis] 17 . However, our study did not identify liver metastases or the time since diagnosis of metastasis < 18 months (i.e. the Tabernero factors) as being prognostic of OS or PFS, and we did not examine mutational status, CEA or ALP levels, or lymphocyte-to-monocyte or neutrophil-to-lymphocyte ratios as potential prognostic factors.
In our study, TAS-102 plus bevacizumab was associated with manageable toxicities, with the most common grade 3-4 AEs being neutropenia, asthenia and nausea/vomiting. The incidence of grade 3-4 neutropenia (45.7%) was lower than that reported in the C-TASK FORCE study (72%) 9 and the Danish study (67%) 10 , and was slightly lower than in previous Japanese real-world studies (48.2-52.4%) [14][15][16] . Furthermore, no patients developed febrile neutropenia in our study, while the incidence of this event was 16% and 6%, respectively, in C-TASK FORCE and the Danish study 9,10 , and 0-3.3% in the Japanese real-world studies [14][15][16] . The lower levels of haematological toxicity observed in our study may have been due to the relatively high proportion of patients who received prophylactic G-CSF therapy (14.3%). Of note, several studies have reported that chemotherapy-induced neutropenia with TAS-102 (with or without bevacizumab) is associated with improved survival outcomes [22][23][24] , which highlights the importance of G-CSF prophylaxis to prevent or manage neutropenia and allow for continued TAS-102 plus bevacizumab treatment without the need for dose reduction.
The limitations of our study include its retrospective, single-arm, single-centre design and its small population size (N = 35). An ongoing international phase III study (SUNLIGHT; NCT04737187) is currently investigating the efficacy and safety of TAS-102 plus bevacizumab versus TAS-102 monotherapy as third-line treatment in patients with refractory mCRC, and has a target enrolment of 490 patients 25 . This open-label, multicentre study aims to further confirm the clinical benefits of TAS-102 plus bevacizumab over TAS-102 monotherapy in a large population of patients with refractory mCRC; results are expected in 2023.
In conclusion, this real-world study confirms the efficacy and safety of TAS-102 plus bevacizumab in patients with refractory mCRC in routine clinical practice, with survival and tolerability outcomes that were generally consistent with previous clinical and real-world studies of patients in this setting.

Methods
Study design. This observational, retrospective, single-centre study was conducted at the A Coruña University Hospital in Spain in patients aged > 18 years with a confirmed diagnosis of mCRC who were refractory or intolerant to standard therapies. Previous treatment included fluoropyrimidine, oxaliplatin and irinotecan-based chemotherapy and anti-EGFR agents (in patients with wild-type RAS/BRAF tumours). Eligible patients had received treatment with TAS-102 plus bevacizumab in routine clinical practice between July 2019 and October 2021, including patients who had previously received treatment with antiangiogenic agents (i.e. bevacizumab and/or aflibercept). Patients who had previously received TAS-102 monotherapy or TAS-102 in combination with antiangiogenic agents other than bevacizumab were excluded.
The standard doses administered at A Coruña University Hospital were TAS-102 30-35 mg/m 2 on days 1-5 and days 8-12 every 28 days plus bevacizumab 5 mg/kg every 14 days. Starting treatment with reduced doses of TAS-102 or administration of prophylactic G-CSF was at the discretion of the treating physician.
The study was approved by the local ethics committee and conducted in accordance with the Declaration of Helsinki. All patients gave their informed consent prior to study inclusion.   www.nature.com/scientificreports/